Why do my pistons look like this?
#1
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Why do my pistons look like this?
Each of the 4 pistons are cleaner along the edge on the intake side of the motor. What's up with this?
Last edited by paul; 05-02-2008 at 03:35 AM.
#2
Mine were like that too. It's from the air/fuel mixture flowing right by it when the valves first open for the intake stroke. Air flows out of the valve and follows the contour of the combustion chamber and it sweeps down onto the piston. It's also clean around the edges of the reliefs in the pistons for the same reason.
Furthermore, you will note the clean spot goes away as you move toward the reliefs in the pistons. That is because your intake valves are extemely shrouded and not much air comes out of that area of the valve. Therefore not a lot of air sweeps down the combustion chamber in these areas and hits the pistons. As you move away from the reliefs, you see another clean spot develop. That's where the valve starts moving some air again.
Furthermore, you will note the clean spot goes away as you move toward the reliefs in the pistons. That is because your intake valves are extemely shrouded and not much air comes out of that area of the valve. Therefore not a lot of air sweeps down the combustion chamber in these areas and hits the pistons. As you move away from the reliefs, you see another clean spot develop. That's where the valve starts moving some air again.
#4
And of course you'll want to add nitrous to keep the rest of the pistons clean too.
Yea I would suggest unshrouding the pockets around the valves a minimum radius of X% the diameter of the face of the valve. For the exhaust a minimum of 25%, for the intakes 30%. That's how mine are. Those numbers are ideal for a NA motor. FI the numbers are more like 30,35, or 35,40. Less compression and more flow is a win/win for FI setups. Mine will go to 30/35 next time the head is off.
Yea I would suggest unshrouding the pockets around the valves a minimum radius of X% the diameter of the face of the valve. For the exhaust a minimum of 25%, for the intakes 30%. That's how mine are. Those numbers are ideal for a NA motor. FI the numbers are more like 30,35, or 35,40. Less compression and more flow is a win/win for FI setups. Mine will go to 30/35 next time the head is off.
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